1. Field of Invention
The present invention relates to a ground fault interrupter for ground fault protection of persons using an electrical appliance. More particularly, the invention relates to GFCI receptacles utilizing a low friction pivotal latch, an end-of-life indicator and reverse wiring protection.
2. Description of Related Art
A ground fault occurs when current improperly flows through a ground line. Such a condition may indicate a shock hazard, even when the current flow is insufficient to trip a main breaker in the building in which the GFCI has been installed. Known ground fault circuit interrupters have been mounted in a receptacle housing with a detector to sense the ground fault condition. A ground fault is often detected by determining whether there is an imbalance in current between the two primary power lines. One or more toroidal coils can encircle the primary power lines to detect an imbalance in the currents in those lines. The imbalance can produce an output voltage from the toroidal coil to trigger a semiconductor circuit that energizes a solenoid coil. The solenoid coil drives an armature to release a latch that otherwise holds a pair of movable electrical contacts against a pair of stationary electrical contacts. When the movable contacts are released, power is disconnected from the terminals of the receptacle protected by the ground fault circuit interrupter (GFCI).
A GFCI generally includes a housing, a tripping means, a reset button, a test button, a mounting strap with a grounding strap and banding screw, a pair of movable contact holders with electrical contacts, a pair of fixed contact holders with electrical contacts, and a control circuit.
GFCIs are widely used to prevent electric shock and fire caused by a ground fault.
In the past, a GFCI receptacle generally utilized a mechanical actuator, which limited the performance of such products, especially insofar as these GFCIs did not provide reverse wiring protection. Examples of mechanical GFCIs include those disclosed in U.S. Pat. No. 5,935,063 and in U.S. Pat. No. 4,802,052.
The GFCI shown in published U.S. Patent Application No. 2006/0018062 A1 has reverse wiring protection that incorporates an electromagnetic tripping means and a corresponding control circuit. A significant disadvantage of this device is the relatively high mechanical resistance in initiating movement of a movable assembly of the device.
In addition, there is no end of life indicator in the above GFCIs which standard UL 943 now requires.
Accordingly, there is a need for a GFCI with an end of life indicator, reverse wiring protection, using a solenoid that easily overcomes frictional forces associated with a releasing latch means.